Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of voice over Internet protocol service provider Vonage (NYSE: VG) were heading for the stratosphere today, gaining as much as 25% in intraday trading after the company announced fourth-quarter results.

So what: Since its IPO, Vonage has been a tough company to love. Large losses, cash burn, the threat of bankruptcy -- these aren't a few of shareholders' favorite things. But Vonage has scrapped its way back, and its fourth-quarter report showed the company continuing to move in the right direction. Adjusted net income came in at $0.06, which easily topped the $0.04 that Wall Street expected. Maybe more importantly, the company announced the addition of 6,000 net new customers, which is the first quarter in more than two years that that number has been positive.

Now what: As a customer of Vonage myself, I have few complaints. As an investor though, I'm inclined to dismiss the stock. After all, there's still plenty of debt to be dealt with, and competitive pressures from the likes of Comcast (Nasdaq: CMCSA), Time Warner Cable (NYSE: TWC), and Cox Communications are very real. However, the company is making definite progress when it comes to profit from operations and cash flow. And while the stock isn't anywhere near the lows of 2009, the current valuation looks far from egregious. I may not be quite ready to give Vonage a full-on thumbs-up, but the stock could be worth a closer look.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.